Papermaking machine



Sept. 6, 1966 A. MORAVEK 3,270,435

PAPERMAKING MACHINE Filed July 24, 1963 United States Patent 3,270,435 PAPERMAKING MACHINE Rudolf A. Moravek, Neenah, Wis., assignor to Kimberly- Clark Corporation, Neenah, Wis., a corporation of Delaware Filed July 24, 1963, Ser. No. 297,452 4 Claims. (Cl. 34-117) My invention relates to papermaking machines and, more particularly, to drying sections for tissue making machines in which the tissue is creped by means of a doctor blade from a heated drier drum.

In tissue making machines, the moist paper Web is generally directed from a felt section to a Yankee drier which is a large steam heated drier drum generally having a diameter of about 12 feet. Tissue creping apparatus including a doctor blade in scraping contact with the outer cylindrical peripheral surface of the drier drum is provided, and the paper Web in traveling with the drier drum on its outer surface is dried and the web is then creped from the drum by the blade for subsequent reeling into roll form. The creping apparatus for such a drier drum generally includes a main upper doctor blade, which is used most of the time for the creping operation, and also a lower auxiliary doctor blade, both blades being fixed in suitable blade holders. It is necessary with such doctor blades, to maintain sharply defined creping angles on the creping edges of the blades for proper creping action; and such a blade, after about /2 hour to 2 /2 hours usage, wears to such an extent that it should be removed from its holder for regrinding and replaced. The creping apparatus, therefore, generally includes the second or lower doctor blade which is put into creping contact with the outer surface of the drier drum just before the upper doctor blade is removed from the surface of the drum for the purpose of replacing the upper doctor blade with a freshly ground blade.

During the replacement of the upper doctor blade in its holder with a newly ground blade and while the lower doctor blade is effective for creping the web from the drier drum, the creped paper web doctored from the drum by the lower blade generally simply goes onto the floor as waste. While the upper blade is being replaced with a freshly ground blade, it would, of course, be possible to stop providing web to the drier, such as by effectively separating the Fourdrinier and felt sections of the machine so that there is no web transfer between them, whereby a web does not pass over the drier drum at this time; however, this is not done because the drier drum would heat up to too high a temperature; and a fresh sheet, when one is started through the machine, would flash or burn when put onto the drier drum. Generally a change from a worn top doctor blade to a fresh blade ordinarily requires only a minute or two; therefore, not much waste is produced with this operation.

After the upper doctor blade has been replaced in its holder with a freshly ground blade, the fresh blade must be moved by means of the holder into doctoring relation with the heated drum. Previously, it was common practice to provide a freshly ground blade with minute serrations or teeth on the doctoring edge riding on the drum, these teeth generally being produced simply by rough filing the doctor edge. The minute saw teeth functioned to cut through the web to begin the creping action as the blade was moved into contact with the drum. These rough edges, however, particularly in connection with drier drums of relatively soft metal, such as bronze, scored the surface of the drum which was very objectionable. Therefore, under present practice, the fresh doctor blade is provided with a very smooth edge, which is not capable of cutting through the web on the drum; and just before the fresh upper blade is moved into contact with the drier drum, production of web by the machine is stopped, such as by separating the belt and Fourdrinier wire so that no web can transfer to the felt section. While the drier drum is free of the sheet (the time required is only 5 to 10 seconds and the drum thus does not become unduly hot), the top doctor blade is moved back against the surface of the drum; and effective connection is re-established between the felt and Fourdrinier wire so that paper web again travels through the felt section onto the drier drum for creping off the drier drum by the top doctor blade. The above mentioned operations require only these few seconds, since a machine tender near the drier watches the operation closely and as soon as he notices that no sheet is traveling over the surface of the drier drum, he immediately moves the top doctor blade back into contact with the drum; and at his signal, another machine tender causes the felt to be put into contact with the Fourdrinier wire to again supply web to the drier drum. At this time, the sheet is creped by the top doctor blade off the drum and initially moves onto the floor; it is immediately taken up by a machine tender, however, and started on the reel of the machine for normal production.

After resumption of creping by the top doctor blade, the bottom doctor should be removed from the surface of the drier drum to prevent undue wear both on the blade and on the drum; and, at this time, it has been found that, unless certain precautions are taken, the bottom doctor becomes unduly heated and scores the surface of the drier drum. A creping doctor blade generally is made of a tempered spring steel of about .012 inch thickness, and it becomes extremely hot due to its frictional contact with the surface of the drier drum when a sheet is not being creped by the blade. Under these conditions, such a doctor blade may heat up to 600 F. to 1000 F. If the doctor blade is maintained in full creping pressure with the drier drum, such high temperatures cause no trouble except for undue uniform wear on blade and drier; however, when such a blade is withdrawn from the surface of the drier drum at the high temperatures that result under the above mentioned conditions, the blade buckles due to its thinness and resultant elastic instability. Waves or scallops exist in the thin blade under these conditions, and these produce high pressure contact areas against the drier surface which score the surface of the drier drum. This scoring is particularly troublesome and acute if the drier drum is made of a relatively soft high heat conducting material such as bronze. The waves in such a blade which buckles due to its elastic instability may have lengths from 2 inches to 8 inches, but generally the length of such waves is 3 inches to 4 inches. A drier drum generally also has a coating on its surface of .00025 inch to .002 inch thickness which is made up of small paper fibers or paper debris and which also may include a special varnish. This coating functions to provide proper creping action by a doctor blade, assuring that the sheet sticks to the drier drum to the proper extent and is removed only from the surface of the drier drum with a proper force for satisfactory creping. This undesired buckling of the thin doctor blade also has the action of non-uniformly cutting through this drier coating; so that where the high points of the buckled blade leave the surface of the drier drum, as the blade is being moved out of contact with the drum, peripheral drum surface areas in which the coating has been removed from the drier drum result, whereby proper creping subsequently is not obtainable.

It is an object of the present invention to provide an improved method and apparatus for preventing such buckling of a lower doctor blade in a tissue making machine so as to prevent the consequent scoring of the drier drum .and uneven cutting of the coating on the drum. More particularly, it is an object to provide apparatus for cooling the lower doctor blade as it is being withdrawn from the surface of the drum, so that the doctor blade does not have the high temperatures causing buckling under these conditions.

The invention consists of the novel constructions, arrangements, devices, and methods for carrying out the above stated objects, and such other objects, as will be apparent from the following description of a preferred form of the invention and manner of carrying out the invention, illustrated with reefrence to the accompanying drawings, wherein:

FIG. 1 is a fragmentary side elevational view of a Yankee drier drum in a papermaking machine, together with upper and lower creping doctors for the drum; and, FIG. 2 is a side elevational view of a shower pipe for directing cooling water or air against the blade of the lower doctor.

Like characters of reference designate like parts in the several views.

Referring now to the drawings, a steam heated Yankee drier drum is illustrated, having an upper doctor 11 and a lower doctor 12 for creping paper web from the drier drum. The drum .10 is of conventional construction; it is heated by means of steam supplied by 'conventional apparatus to the drum; and it is rotated by conventional driving mechanism in the direction indicated by the arrow 13. The drum 10 is part of a conventional papermaking machine having a Fourdrinier section and a felt section, in addition to the drying section comprising the drum 10'. In accordance with well-known practice, the paper web is formed in the Fourdinier sect-ion and is transferred to the felt section by having a felt and a Fourdrinier wire in running contact, and the Web A is subsequently transferred to the surface of the drum 10 by holding a felt in contact with the surface of the drum 10 as by means of a pressure roll (not shown).

The upper doctor 11 comprises a doctor blade 14 which is adapted to have scraping contact with the drum 10 and which is held in position to have such contact by a holder 15. The blade 14 may be of tempered spring steel of a thickness about .012 inch, for example; and in accordance with conventional practice, the blade may protrude, for example, about /2 inch from the end of its holder 15. The holder 15 is made to be very stiff, having a relatively massive cross section and being of cast iron, for example, in view of the fact that the holder extends unsupported for the complete width of the drier drum 10, which may be 180' inches or more.

The holder ;15 is rotatably supported with respect to the papermaking machine and the drier drum 10 by means of a pair of end shafts 16 on the two ends of the holder, each shaft being rotatably disposed in a frame 17. Each frame 17 has a lower arm 18 through which a threaded stud 19 extends. The stud 19 is connected by means of a clevis 20 with a fixed machine part, and nuts 21 and 22 are provided on the stud 19 for the purpose of adjustably fixing the arm 18 with respect to the stud 19. Each of the frames 17 on the two ends of the blade holder 15 is provided with an upwardly extending threaded stud 23 passing through a fixed arm 24, and a pair of nuts 25 and 26 are provided on the stud 23 for the purpose of fixing the stud 2 3 with respect to the stationary arm 24. The location of the holder 15 with respect to the outer cylindrical surface of the drier drum may be adjusted, as is obvious, by adjusting the nuts 21, 22, 25 and 26 on their studs 19 and 23.

The holder .15 may be rotated for the purpose of moving the blade 14 into and out of contact with the surface of the drier drum 10 by means of a pair of air motors 27. Each of the air motors 27 has a piston rod 28 which is connected to .an arm 29 fixed to one of the end shafts 16, and the upper end of each air motor 27 is fixed with respect to a fixed part of the paper-making machine.

The construction of the lower doctor 12 is generally similar to that of the upper doctor 11. The lower doctor 12 comprises the blade 30' and its holder 31 having a pair of end shafts 32. Opposite frames 33 are provided for supporting the holder 31 by means of the shafts 3-2, and each frame is adjustably fixed with respect to the papermaking machine by means of threaded studs 34 and 35 having nuts 36, 37, 38, and 3-9 thereon. A pair of air motors 40 are fixed at their upper ends with respect to the paper making machine frame and each has its piston rod 41 connected to an arm 42 that is fixed on one of the shafts 32.

A water shower pipe 43 is fixed by any suitable brackets with respect to the papermaking machine in susbtantially the position illustrated in FIG. 1, extending along and opposite the blade 30. The pipe 43 is closed at one end by means of a cap 44 and is provided with a plurality of spaced openings 45 therethrough, and the pipe is so located and the openings 45 are so directed that water passing through the openings 45 impinge-s on the blade 30 when the blade is in contact with the surface of the drier drum 10. The pipe 43 is connected to a Water supply pipe 46 through a flexible hose connection 47 and a valve 48.

In operation, paper web A travels on the surface of the drum 10 as the drum 10 rotates, the paper web being formed on a Fourdrinier section and being partially dewatered by means of a felt section which, together with the drum 10, constitute parts of the papermaking machine. The upper blade 14 carried by the holder .15 is during normal operation maintained in scraping contact with the surface of the drum 10' by means of the motors 27 acting through the piston rods 28 and arms 29, and the paper web is creped from the surface of the drum by the blade 14 for reeling on a suitable reel (not shown).

As has been previously explained, a doctor blade such as either of the blades 14 and 30, should have certain angles on its acting edge in order to be eifective. After the blade 14 has been in use for some time, such as /2 hour to 2 /2 hours, the acting edge in contact with the surface of the drier 11 is so worn that creping is not satisfactory, and the blade 14 must, therefore, be replaced. At this time, the motors 40 are supplied with air under pressure and are effective to rotate the holder 31 in a counterclockwise direction about its end shafts 32 so as to move the lower doctor blade 30 into contact with the surface of the drum .10. The motors 27 are then supplied with air under pressure so that they .are effective through the piston rods 28 and arms 29 to rotate the holder 15 in the clockwise direction as seen in FIG. 1 to move the blade 14 out of contact with the surface of the drum 10. The sheet is then creped from the surface of the drum 10 by the blade 30 and is allowed to accumulate on the floor as waste.

The upper doctor blade 14 is then replaced by a newly ground blade 14 in the holder v15. The holders 15 and 31 are both of conventional construction which is such that they may be readily disassembled to allow an easy replacement of the doctor blades carried by them. This blade replacement requires a minute or two, and the motors 27 are then supplied with pressure air in such manner that the holder 15 is rotated in the counterclockwise direction to move the blade 14 back into contact with the surface of the drum 10. As has been previously explained, the production of paper web is temporarily stopped, such as for 5 to 10 seconds, just as the upper doctor blade is moved back into creping position with respect to the surface of the drum 10. After the production of web is resumed, the upper doctor 14 again crepes the web from the surface of the drum 10 and the web is wound on the reel (not shown) for normal operation.

The lower doctor blade 30 should at this time be removed from the surface of the drum 10 and unless measures are taken to keep the temperature of the blade 30 down, the blade 30 will increase in temperature to such a degree that it will tend to buckle and will make uneven contact with the surface of the drier drum when being withdrawn from the drum, as has been previously mentioned. The valve 48 is opened at this time so as to provide cooling water to the pipe 43, and the water is sprayed through the openings 45 onto the doctor blade 30. The water thus sprayed onto the blade 30 keeps the temperature of the blade down so that it does not buckle and rather stays in a single plane. The motors 40 are then supplied with air under pressure in such manner as to rotate the holder 31 in a clockwise direction and draw the blade 30 away from the surface of the drum 10. Since the blade 30* stays in a single plane, without buckling, it is uniformly drawn away from the surface of the drum and does not unevenly gouge out the surface of the drum or unevenly remove the drier coating; and, therefore, the surface of the drum 10 remains uniform for subsequent even creping action by the upper doctor blade 14.

I wish it to be understood that the invention is not to be limited to the specific constructions, arrangements, devices and methods above described, except only insofar as the claims may be so limited, as it will be apparent to those skilled in the art that changes may be made without departing from the principles of the invention. In particular, it will be apparent that although I have mentioned water as being supplied to the spray pipe 43, other cooling fluids may instead be supplied, such as air.

What is claimed is:

1. In a papermaking machine, the combination of a heated rotatable drier drum for drying a web of paper on the surface of the drum, a pair of thin metal doctor blades for doctoring the paper web off the drum, means for moving each of said doctor blades into doctoring engagement with the exterior surface of the drum along spaced lines on the drum surface so that one blade constitutes a leader doctor blade and the other blade constitutes a follower doctor blade with respect to drum rotation, and means for spraying a cooling fluid on said follower doctor blade to prevent buckling of the blade as it is moved out of doctoring engagement with the drier drum.

2. In a papermakin-g machine, the combination of a heated rotatable drier drum for drying a web of paper on the surface of the drum, a pair of thin metal doctor blades for doctoring the paper web off the drum, a rotatably mounted rigid holder for each of said doctor blades, means for moving each of said holders and thereby said blades so that the latter have doctoring engagement with the exterior surface of the drum along spaced lines on the drum surface whereby one blade constitutes a leader doctor blade and the other blade constitutes a follower doctor blade with respect to drum rotation, at

source of cooling fluid, and a spray pipe connected with said source and extending along and adjacent said follower blade and having a plurality of openings in the pipe so directed that cooling fluid is discharged from the pipe onto said follower doctor blade whereby to prevent buckling of the follower blade as it is moved out of doctoring engagement with the drier drum.

3. In a method for operating a papermaking machine having a rotatable heated drier drum with a leader and a follower thin metal doctor blade each adapted to be moved into paper creping engagement with the exterior surface of the drum, the steps which comprise, moving the leader doctor blade out of engagement with the drum while paper web is traveling on the surface of the drum to allow replacement of the blade while holding the follower doctor blade in contact with the drum to crepe the web from the drum, moving the upper doctor blade into creping engagement with the drum after replacing the blade to crepe the paper web from the drum, and thereafter moving the follower doctor blade out of contact with the drum and during said movement spraying the follower doctor blade with a cooling fluid so as to prevent buckling of the follower doctor blade.

4. In a method of operating a papermaking machine having a rotatable heated drier drum with a leader and a follower thin metal doctor blade each adapted to be moved into creping engagement with the exterior surface of the drum, the steps which comprise, moving the leader doctor blade out of engagement with the drum while paper web is traveling on the surface of the drum While holding the follower doctor blade in contact with the drum to crepe the web from the drum, replacing the leader doctor blade, thereafter moving the leader doctor blade back into creping engagement with the drum while causing a brief cessation of application of paper web to the drum, and thereafter moving the follower doctor blade out of contact with the drum and spraying the follower doctor blade with cooling fluid during such movement whereby to prevent buckling of the follower doctor blade.

References Cited by the Examiner UNITED STATES PATENTS 1,605,067 11/1926 Read 34-120 X 3,097,933 7/1963 Kellogg et al. 34-110 X 3,166,464 1/1965 Eolkin 34-ll0 X FREDERICK L. MA'I'IESON, JR., Primary Examiner.

JOHN J. CAMBY, Examiner. 

1. IN A PAPERMAKING MACHINE, THE COMBINATION OF A HEATED ROTATABLE DRIER DRUM FOR DRYING A WEB OF PAPER ON THE SURFACE OF THE DRUM, A PAIR OF THIN METAL DOCTOR BLADES FOR DOCTORING THE PAPER WEB OFF THE DRUM, MEANS FOR MOVING EACH OF SAID DOCTOR BLADES INTO DOCTORING ENGAGEMENT WITH THE EXTERIOR SURFACE OF THE DRUM ALONG SPACED LINES ON THE DRUM SURFACE SO THAT ONE BLADE CONSTITUTES A LEADER DOCTOR BLADE AND THE OTHER BLADE CONSTITUTES A FOLLOWER DOCTOR BLADE WITH RESPECT TO DRUM ROTATION, AND MEANS FOR SPRAYING A COOLING FLUID ON SAID FOLLOWER DOCTOR BLADE TO PREVENT BUCKLING OF THE BLADE AS IT IS MOVED OUT OF DOCTORING ENGAGEMENT WITH THE DRIER DRUM. 